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Posted: 5/1/2021 12:29:43 PM EDT
[#1]
Quote HistoryQuoted: Not torqued = not the same. Also, butted against an upper receiver which is between shooter and breach is not the same as open direct line from breach cap to shooter. Also, ratio of amount of thread engagement to amount of pressure is NOT even close to the same. Not sure what you're trying to prove, but you're digging your hole deeper. Is an F150 pulling 10k pounds the same as an F450 pulling a john boat? I mean, they both have engines, four tires, and a trailer hitch, right? eta: Not trying to be a smart ass, as I enjoy discussing minutiae too. It could come down to your definition of "same". Yes, the breach is basically threaded together. No, they're not the same re: strength of the joint in the respective designs and executions regardless of containment. I am not trying to "prove" anything. I wasn't the one who brought the similarity of the threaded breach on an AR-15 to this thread. I also keep saying I am not asking about containment, yet it is a point that appears in each reply. Even after I specifically exclude it. Nor have I tried to compare the "ratio of amount of thread engagement to amount of pressure", yet now it appears. I made a VERY basic comparison. The AR-15 has a breech section threaded on to the barrel, similar to the Serbu in this thread. Again, not asking about containment in an over-pressure event. |
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Posted: 5/1/2021 1:37:19 PM EDT
[#2]
Quote HistoryQuoted: Damn. Firing .50 SLAP mystery-meat rounds just got crossed off of my list. That was never on my list. |
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Posted: 5/1/2021 3:03:42 PM EDT
[#3]
Quote HistoryQuoted: If the threads failed at 85k, which per the designer is the failure point, then that was the maximum pressure achieved. Pressure was released at that point. How much pressure would that round have built in a stronger gun? Who knows, and irrelevant. Quote HistoryQuoted: If the threads failed at 85k, which per the designer is the failure point, then that was the maximum pressure achieved. Pressure was released at that point. How much pressure would that round have built in a stronger gun? Who knows, and irrelevant. Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. eta: What you are suggesting is that an 86k PSI round would have resulted in the same damage/carnage/failure seen in the video as a 100k (or higher) PSI round, and I am saying that is unequivocally wrong. I’m also suspicious of a number given over the phone without an analysis of the failing parts. 85k may be the design pressure, which IMO still makes it a crap gun since it fails lethally, but this gun may have had a manufacturing defect and/or fatigue that caused it to fail at 55k on that particular shot. Shallow threads on the cap or barrel, bad heat treat on the barrel, etc. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. |
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Posted: 5/1/2021 3:10:10 PM EDT
[#4]
Quote HistoryQuoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. Yeah, I'm thinking the SLAP round that produced the enormous fireball is likely the round that did the damage that doomed that rifle, and it still took 2 additional rounds to finish it off. |
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Posted: 5/1/2021 3:12:35 PM EDT
[#5]
Quote HistoryQuoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. Quote HistoryQuoted: Quoted: If the threads failed at 85k, which per the designer is the failure point, then that was the maximum pressure achieved. Pressure was released at that point. How much pressure would that round have built in a stronger gun? Who knows, and irrelevant. Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. I’m also suspicious of a number given over the phone without an analysis of the failing parts. 85k may be the design pressure, which IMO still makes it a crap gun since it fails lethally, but this gun may have had a manufacturing defect and/or fatigue that caused it to fail at 55k on that particular shot. Shallow threads on the cap or barrel, bad heat treat on the barrel, etc. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. I suspect if all the rounds were overpressure, and repeated loads caused fatigue failure, there should have been some deformation of the threads, at the very least making it difficult to screw and unscrew. |
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Posted: 5/1/2021 3:18:24 PM EDT
[#6]
Quote HistoryQuoted: Since most people can't get a 300rum barrel to live thru more than 800 rounds sub moa, and the fact that all steel has a stress/cycle life, and knowing this rifle spent most of its life shooting the original factory 180/3250fps ammo,(long ago detuned to 180/3200by Remington) it has been living on the edge its entire life, I see no reason to keep pushing it, especially since if I died tomorrow one of my kids would get it, and they would have no clue about action life expectancy...sure I could throw a new bolt in it, along with more smith labor, but seems like a waste of money considering the price of a tenacity action...which also eliminates sending the action stateside every time it needs a new barrel...at close to 200 bucks shipping round trip...Oh and most quality smiths are 8-12 months out for any work....swapping actions was an easy choice...  That's not how any of this works. Accuracy degradation with an overbore cartridge is in no way a result of action/receiver "cycling", and 100% a result of barrel (specifically throat) wear. I can't believe you would think otherwise....and suggesting the rifle has been "living on the edge its entire life" is comical. The brass may be living on the edge. Hell, primer pockets may be living on the edge....but as long as you are staying in SAAMI specs, that 700 doesn't give a damn. |
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Posted: 5/1/2021 3:19:46 PM EDT
[#7]
Quote HistoryQuoted: there should have been some deformation of the threads, at the very least making it difficult to screw and unscrew. That's a very good point, and it would be interesting to ask the guy in the video... |
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Posted: 5/1/2021 3:22:56 PM EDT
[#8]
Quote HistoryQuoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. Quote HistoryQuoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. This could be correct. It's also possible the gun was weakened after having several hundred rounds through it. The 85k is a manufacturer CLAIM. I'm personally not going as far as blaming the gun manufacturer outright, but I absolutely will suggest it's well worth considering regardless of Scott & Serbu blaming the ammo. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. You're missing his point. He's talking about guns being designed to fail non-lethally. Think of it like a car. Car-manufacturers design and test cars, such that people are less likely to die in the case of an accident. That includes techniques like crumple-zones. Crash tests are important too - you wouldn't want the steering-wheel column acting like a spear through the chest in a 20mph front-end crash. With guns, there are numerous techniques used to reduce the likelihood an over-pressure event would result in severe injury or death. https://www.youtube.com/watch?v=71OGayW7CnI Even if we do primarily blame the ammo, it's still perfectly valid to critique the gun itself, or consider ways the design could be improved to reduce the chances of a similar failure killing someone else. Similar to a car accident, you want the car to protect the occupant from accidents that aren't the car's fault or driver's fault. |
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Posted: 5/1/2021 3:35:26 PM EDT
[#9]
Think of it like a car. Car-manufacturers design and test cars, such that people are less likely to die in the case of an accident. That includes techniques like crumple-zones. Crash tests are important too - you wouldn't want the steering-wheel column acting like a spear through the chest in a 20mph front-end crash. I know exactly the direction he was going with his response...and this wasn't a 20 MPH front end collision. This was more like hitting a concrete barrier at 175 MPH in a Z06, and then blaming Chevrolet for your injuries. History has shown us time and time again that you can't beat Darwin, he is always taking notes. |
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Posted: 5/1/2021 3:36:29 PM EDT
[#10]
Quote HistoryQuoted: That's a very good point, and it would be interesting to ask the guy in the video... Quote HistoryQuoted: Quoted: there should have been some deformation of the threads, at the very least making it difficult to screw and unscrew. That's a very good point, and it would be interesting to ask the guy in the video... I just watched the vid, finally, and the only case he shows being removed was the APIT that didn’t penetrate the hydrant and he had to pry that case out. |
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Posted: 5/1/2021 3:44:22 PM EDT
[#11]
Guy is lucky to be alive. What bothers me about the entire thing is how the gun blew up. Failure should be away from the shooter. That end cap should not be the weak spot.
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Posted: 5/1/2021 3:52:24 PM EDT
[#12]
Quote HistoryQuoted: Since most people can't get a 300rum barrel to live thru more than 800 rounds sub moa, and the fact that all steel has a stress/cycle life, and knowing this rifle spent most of its life shooting the original factory 180/3250fps ammo,(long ago detuned to 180/3200by Remington) it has been living on the edge its entire life, I see no reason to keep pushing it, especially since if I died tomorrow one of my kids would get it, and they would have no clue about action life expectancy...sure I could throw a new bolt in it, along with more smith labor, but seems like a waste of money considering the price of a tenacity action...which also eliminates sending the action stateside every time it needs a new barrel...at close to 200 bucks shipping round trip...Oh and most quality smiths are 8-12 months out for any work....swapping actions was an easy choice... No, steel has an endurance limit. If the bolt is designed to stay below that, it can withstand an infinite number of load cycles. Aluminum does not have an endurance limit so it will eventually fail even if the load is small. However that doesn't mean you can't exceed the endurance limit in your design. You simply design it so that the failure would require so many cycles you will never realistically hit it. This is how all Al parts are designed. Given the 700 action is one of the most prevalent and reliable actions out there, I think you are worrying about nothing. Just because barrels wear out from being directly exposed to very hot gasses and friction from bullets pushing through it at over 3200fps does not mean your lugs will fail  If the cap is designed such that it would shear at 85 ksi, that is not a lot of margin since the endurance limit for steel is usually ~ .4x its UTS. That means every round was taking away life with this cap. Like I said, that may be acceptable if you shoot normal ammo as you would never reach the fatigue limit but when you throw overpressure rounds in, it's a ticking time bomb. Also notice it sheared on the female threads. Usually threaded connections will shear on the male threads if the materials are of equal strength since the male threads have less surface area. Thus the cap was made from a weaker steel than the barrel. |
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Posted: 5/1/2021 3:53:23 PM EDT
[#13]
Add me to the "this rifle design is crap" camp. Most rifles are designed with the idea of trying to keep the shooter safe when the rifle explodes. Militaries expect to they will have bad ammo occasionally and commercial companies expect to deal with fools. This rifle's design philosophy appears to be, keep everything contained at all cost. And if it fails just hope for the best.
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Posted: 5/1/2021 4:14:56 PM EDT
[#14]
Quote HistoryQuoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. eta: What you are suggesting is that an 86k PSI round would have resulted in the same damage/carnage/failure seen in the video as a 100k (or higher) PSI round, and I am saying that is unequivocally wrong. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. Quote HistoryQuoted: Quoted: If the threads failed at 85k, which per the designer is the failure point, then that was the maximum pressure achieved. Pressure was released at that point. How much pressure would that round have built in a stronger gun? Who knows, and irrelevant. Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. eta: What you are suggesting is that an 86k PSI round would have resulted in the same damage/carnage/failure seen in the video as a 100k (or higher) PSI round, and I am saying that is unequivocally wrong. I’m also suspicious of a number given over the phone without an analysis of the failing parts. 85k may be the design pressure, which IMO still makes it a crap gun since it fails lethally, but this gun may have had a manufacturing defect and/or fatigue that caused it to fail at 55k on that particular shot. Shallow threads on the cap or barrel, bad heat treat on the barrel, etc. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. There are three kinds of people in this thread: 1. People who know stuff. 2. People who are learning stuff from the people who know stuff. 3. People who bought one of these terrible guns and must white knight. Which one are you? ETA: Once pressure is released, that’s it. This isn’t a high order explosive we are dealing with. The peak pressure was the pressure at the time of failure. |
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Posted: 5/1/2021 4:39:12 PM EDT
[#15]
Quote HistoryQuoted: Guy is lucky to be alive. What bothers me about the entire thing is how the gun blew up. Failure should be away from the shooter. That end cap should not be the weak spot. Maybe a design like this would have been better.....  or this....  Every design has a weak spot....... some leave people dead ...... |
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Posted: 5/1/2021 4:49:50 PM EDT
[#16]
Quote HistoryQuoted: That was never on my list. Quote HistoryQuoted: Quoted: Damn. Firing .50 SLAP mystery-meat rounds just got crossed off of my list. That was never on my list. What, you’ve never fancied setting off a potential pipe-bomb right in front of your face? 
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Posted: 5/1/2021 5:01:12 PM EDT
[#17]
Quote HistoryQuoted: What, you’ve never fancied setting off a potential pipe-bomb right in front of your face? Quote HistoryQuoted: Quoted: Quoted: Damn. Firing .50 SLAP mystery-meat rounds just got crossed off of my list. That was never on my list. What, you’ve never fancied setting off a potential pipe-bomb right in front of your face? I've done some sketchy stuff with guns and I might even reload for my 50's one day but I have never had the desire to shoot the oddball gunshow maybe surplus ammo floating around. The Talon ammo I bought is about as sketchy as I'm willing to go. |
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Posted: 5/1/2021 5:02:22 PM EDT
[#18]
Quote HistoryQuoted: No, steel has an endurance limit. If the bolt is designed to stay below that, it can withstand an infinite number of load cycles. Aluminum does not have an endurance limit so it will eventually fail even if the load is small. However that doesn't mean you can't exceed the endurance limit in your design. You simply design it so that the failure would require so many cycles you will never realistically hit it. This is how all Al parts are designed. Given the 700 action is one of the most prevalent and reliable actions out there, I think you are worrying about nothing. Just because barrels wear out from being directly exposed to very hot gasses and friction from bullets pushing through it at over 3200fps does not mean your lugs will fail If the cap is designed such that it would shear at 85 ksi, that is not a lot of margin since the endurance limit for steel is usually ~ .4x its UTS. That means every round was taking away life with this cap. Like I said, that may be acceptable if you shoot normal ammo as you would never reach the fatigue limit but when you throw overpressure rounds in, it's a ticking time bomb. Also notice it sheared on the female threads. Usually threaded connections will shear on the male threads if the materials are of equal strength since the male threads have less surface area. Thus the cap was made from a weaker steel than the barrel. The cap is not designed to shear at 85k psi. It’s proofed to 85k psi. That means something very different. 30-06 proof pressure is 84k psi. |
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Posted: 5/1/2021 5:04:47 PM EDT
[#19]
 RN-50 Blow-Up |
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Posted: 5/1/2021 5:08:39 PM EDT
[#20]
Quote HistoryQuoted: Maybe a design like this would have been better..... https://www.thefirearmblog.com/blog/wp-content/uploads/2015/07/762d15.jpg or this.... https://images.guns.com/wordpress/2014/02/buying-reloads-1.jpg Every design has a weak spot....... some leave people dead ...... Quote HistoryQuoted: Quoted: Guy is lucky to be alive. What bothers me about the entire thing is how the gun blew up. Failure should be away from the shooter. That end cap should not be the weak spot. Maybe a design like this would have been better..... https://www.thefirearmblog.com/blog/wp-content/uploads/2015/07/762d15.jpg or this.... https://images.guns.com/wordpress/2014/02/buying-reloads-1.jpg Every design has a weak spot....... some leave people dead ...... What injuries did the shooters suffer in those situations? |
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Posted: 5/1/2021 5:12:09 PM EDT
[#21]
Quote HistoryQuoted: The cap is not designed to shear at 85k psi. It’s proofed to 85k psi. That means something very different. 30-06 proof pressure is 84k psi. I don't know if that really matters since it doesn't appear the cap failed. It was the threads on the barrel that failed. |
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Posted: 5/1/2021 5:13:50 PM EDT
[#22]
Quote HistoryQuoted: What, you’ve never fancied setting off a potential pipe-bomb right in front of your face? Technically, all firearms are really just potential pipe bombs. A 50 just happens to be much more potent than most. |
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Posted: 5/1/2021 5:15:03 PM EDT
[#23]
Quote HistoryQuoted: What injuries did the shooters suffer in those situations? Quote HistoryQuoted: Quoted: Quoted: Guy is lucky to be alive. What bothers me about the entire thing is how the gun blew up. Failure should be away from the shooter. That end cap should not be the weak spot. Maybe a design like this would have been better..... https://www.thefirearmblog.com/blog/wp-content/uploads/2015/07/762d15.jpg or this.... https://images.guns.com/wordpress/2014/02/buying-reloads-1.jpg Every design has a weak spot....... some leave people dead ...... What injuries did the shooters suffer in those situations? I'm sure they were both A-OK ....... I believe you are missing the point of my post.....when extreme overpressure turns a firearm into a fragmentation grenade, the inherent safety built into any design is out the window |
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Posted: 5/1/2021 5:18:18 PM EDT
[#24]
Quote HistoryQuoted: I'm sure they were both A-OK ....... Quote HistoryQuoted: Quoted: Quoted: Quoted: Guy is lucky to be alive. What bothers me about the entire thing is how the gun blew up. Failure should be away from the shooter. That end cap should not be the weak spot. Maybe a design like this would have been better..... https://www.thefirearmblog.com/blog/wp-content/uploads/2015/07/762d15.jpg or this.... https://images.guns.com/wordpress/2014/02/buying-reloads-1.jpg Every design has a weak spot....... some leave people dead ...... What injuries did the shooters suffer in those situations? I'm sure they were both A-OK ....... Is that an "I don't know?" Every design can fail. Good designs fail with lacerations to the arms, maybe some extremity nerve damage. Bad ones fail with substantial shrapnel penetrating the neck, and skull fractures. |
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Posted: 5/1/2021 5:22:21 PM EDT
[#25]
Quote HistoryQuoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. eta: What you are suggesting is that an 86k PSI round would have resulted in the same damage/carnage/failure seen in the video as a 100k (or higher) PSI round, and I am saying that is unequivocally wrong. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. Ummm. If the threads let go at 85k, the pressure never got above 85k. Not saying that the potential energy in the round could not have produced pressure higher than 85k, but that doesn't change the fact previously stated. As a matter of fact, I did work on a special sabot gun that used smokeless powder to compress hydrogen/oxygen to the point of combustion. They controlled the pressure with a shear plate. When the plate sheared, they knew how much pressure was released into the bore behind the projectile. So, that is exactly how pressure peaks work. (there is gas volume/expansion rate, etc after that fact but peak pressure doesn't rise above the failure of the vessel) Besides that, if the manufacturer mentioned that the threads would do that at 85k, that is NOT an appropriate safety margin for firearms. |
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Posted: 5/1/2021 5:59:41 PM EDT
[#26]
Holy crap that was one hell of a bang
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Posted: 5/1/2021 6:14:25 PM EDT
[#27]
Quote HistoryQuoted: The cap is not designed to shear at 85k psi. It’s proofed to 85k psi. That means something very different. 30-06 proof pressure is 84k psi. CoC 6 Removed --- Edited by brassDid you even watch the video? Have you followed this thread at all?? Serbu said the cap would shear at 85 ksi. 50 BMGs are proofed at 65 ksi. Normal ball rounds are ~ 55 ksi. |
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Posted: 5/1/2021 7:53:27 PM EDT
[#28]
Quote HistoryQuoted: I like the guy. I bought the shirt to support him. But man, he said several times "I had no way of knowing that round was unsafe". Come on man, this is exactly why you don't shoot ammo of unknown origin. He mentioned several times in his videos how much the rounds cost, but says it in a way that indicates that he didn’t buy them. Perhaps given to him by someone he trusts? |
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Posted: 5/1/2021 8:00:38 PM EDT
[#29]
Quote HistoryQuoted: That's a very good point, and it would be interesting to ask the guy in the video... Quote HistoryQuoted: Quoted: there should have been some deformation of the threads, at the very least making it difficult to screw and unscrew. That's a very good point, and it would be interesting to ask the guy in the video... I agree. Great point and interesting to think if Scott had noticed anything different about screwing the cap on that last time. It would seem that, if the previous round or two had damaged the threads, it may have been difficult to screw or unscrew the cap. It also wouldn’t surprise me if it wasn’t common for the cap to get gritty or dirty (or get hot and experience some “swelling”) and sometimes just feel different than an unfired gun would. |
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Posted: 5/1/2021 8:02:29 PM EDT
[#30]
Quote HistoryQuoted: Guy is lucky to be alive. What bothers me about the entire thing is how the gun blew up. Failure should be away from the shooter. That end cap should not be the weak spot. Welcome to the conversation that’s been going on for 7+ pages. |
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Posted: 5/1/2021 8:10:18 PM EDT
[#31]
Quote HistoryQuoted: CoC 6 Removed --- Edited by brassDid you even watch the video? Have you followed this thread at all?? Serbu said the cap would shear at 85 ksi. 50 BMGs are proofed at 65 ksi. Normal ball rounds are ~ 55 ksi. Quote HistoryQuoted: Quoted: The cap is not designed to shear at 85k psi. It’s proofed to 85k psi. That means something very different. 30-06 proof pressure is 84k psi. CoC 6 Removed --- Edited by brassDid you even watch the video? Have you followed this thread at all?? Serbu said the cap would shear at 85 ksi. 50 BMGs are proofed at 65 ksi. Normal ball rounds are ~ 55 ksi. Where did Serbu say that? |
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Posted: 5/1/2021 8:32:42 PM EDT
[#32]
Quote HistoryQuoted: CoC 6 Removed --- Edited by brassDid you even watch the video? Have you followed this thread at all?? Serbu said the cap would shear at 85 ksi. 50 BMGs are proofed at 65 ksi. Normal ball rounds are ~ 55 ksi. Quote HistoryQuoted: Quoted: The cap is not designed to shear at 85k psi. It’s proofed to 85k psi. That means something very different. 30-06 proof pressure is 84k psi. CoC 6 Removed --- Edited by brassDid you even watch the video? Have you followed this thread at all?? Serbu said the cap would shear at 85 ksi. 50 BMGs are proofed at 65 ksi. Normal ball rounds are ~ 55 ksi. If I recall correctly, there is no SAAMI proof or operating pressure for .50BMG as it is not a "sporting" cartridge. If there is a proof pressure in the USA I could not find it with a basic search. CIP does have it: https://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/50-browning-en.pdf Depending on your conversion to PSI (14.5 or 14.7 and some rounding that CIP does) the Operating Pressure is just under 55,000PSI and the Proof Pressure is approximately 67,000PSI The .50BMG is old and as such is relatively low pressure cartridge. |
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Posted: 5/1/2021 8:45:24 PM EDT
[#33]
SLAP rounds should not be fired in chambers not throated for SLAP. You are jamming the sabot into the lands and grooves. Sometimes you get over pressure, sometimes not.
I've chambered SLAP and extracted the round and found the sabot set back up to .100", sometimes a little less. M2's have a generous chamber and can handle a SLAP round. Rifles should not be loaded with SLAP. We throated chambers for SLAP at Barrett a long time ago to play with. I believe it was 5 barrels to test. Accuracy sucks with SLAP rounds. Nice rounds to have in a collection. I have a SLAP and SLAP-T round for the collection. Along with an Athena round. Mark over engineers anything he builds. I've fired a bunch of his different designs when I worked for him. I wouldn't hesitate to fire M33 ball or M8 AP through the RN-50 |
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Posted: 5/1/2021 10:10:27 PM EDT
[#34]
Quote HistoryQuoted: Where did Serbu say that? Listening is fundamental. And it has only been mentioned like 10x in this thread. https://youtu.be/1449kJKxlMQ?t=303 |
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Posted: 5/1/2021 10:13:16 PM EDT
[#35]
Quote HistoryQuoted: If I recall correctly, there is no SAAMI proof or operating pressure for .50BMG as it is not a "sporting" cartridge. If there is a proof pressure in the USA I could not find it with a basic search. CIP does have it: https://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/50-browning-en.pdf Depending on your conversion to PSI (14.5 or 14.7 and some rounding that CIP does) the Operating Pressure is just under 55,000PSI and the Proof Pressure is approximately 67,000PSI The .50BMG is old and as such is relatively low pressure cartridge. https://www.google.com/search?q=proof+pressure+50+bmg+psi&sxsrf=ALeKk035O5xgpYYpf8csq4pJ1CuhMP3lqg%3A1619921444645&ei=JAqOYNTkJrnP0PEP6Pys-A0&oq=proof+pressure+50+bmg+psi&gs_lcp=Cgdnd3Mtd2l6EAMyBQghEKABOgcIABBHELADOggIIRAWEB0QHjoFCCEQqwJQsLIBWP-4AWCVuwFoAXACeACAAXSIAbADkgEDNC4xmAEAoAEBqgEHZ3dzLXdpesgBCMABAQ&sclient=gws-wiz&ved=0ahUKEwjUhpbS9anwAhW5JzQIHWg-C98Q4dUDCA4&uact=5 Either way, 65 or 67, not sure what your point is
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Posted: 5/1/2021 10:31:56 PM EDT
[#36]
Quote HistoryQuoted: Yea....the only thing these 2 have in common is that they are both threads that are located on guns, horrible comparison.  Quote HistoryQuoted: Quoted: Quoted: Barrel extension attached to barrel how? With a hell of a lot more thread engagement, and an actual torque spec, with a hell of a lot less bolt thrust, and also with a big hunk of cast or forged aluminum preventing it from traveling toward your face. There is no getting around how bad this design is. Yea....the only thing these 2 have in common is that they are both threads that are located on guns, horrible comparison.  This. |
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Posted: 5/1/2021 10:38:59 PM EDT
[#37]
Quote HistoryQuoted: Listening is fundamental. And it has only been mentioned like 10x in this thread. https://youtu.be/1449kJKxlMQ?t=303 Quote HistoryQuoted: Quoted: Where did Serbu say that? Listening is fundamental. And it has only been mentioned like 10x in this thread. https://youtu.be/1449kJKxlMQ?t=303 I'm not sure if you're aware of it but that isn't Mark Serbu. What has been quoted throughout this thread is third hand information from the guy that almost killed himself with counterfeit ammunition. |
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Posted: 5/1/2021 10:43:52 PM EDT
[#38]
Quote HistoryQuoted: I'm not sure if you're aware of it but that isn't Mark Serbu. What has been quoted throughout this thread is third hand information from the guy that almost killed himself with counterfeit ammunition. It's also a guy who never blamed Mark and blamed himself. If you have better evidence to prove otherwise show it, until then it's just your baseless conjecture vs the words of a stand up guy who is also praised by Mark in Mark's video today. |
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Posted: 5/1/2021 11:11:43 PM EDT
[#39]
As several others in this thread have pointed out, the cap that threads over the barrel is a poor design. There is not enough thread engagement, you get peak strength at 1.5 x Diameter. On typical course threads that is in the ballpark of 8-12 full turns of engagement vs the 3-4 shown in pictures.
Again as has been stated, 60 degree v threads should be torqued/stretched and not just hand tightened. loose threads are subject to shock loading that isn't evenly distributed, which can cause fatigue and failure/shearing. The most glaringly obvious problem with this design is the cap that threads Over the breach instead of Into the breach. - It looks like the cap has about a 1 1/4" inside diameter, it threads over the outside of the barrel and creates a pretty much airtight seal. - A normal 50 bmg is in the ballpark of 55ksi developing 20,000 lbs of bolt thrust (based on a 0.680" case I.D.), an 85ksi load would produce about 31,000 lbs of thrust which may or may not be enough to cause a failure in this gun. Not much safety factor but at least there is some. - What nobody seems to be taking into account is what happens in the event of a case rupture or even a pierced primer. All of that pressure is going to vent into that sealed up cap. That means that we now have 55,000+ psi pushing against the 1 1/4" diameter on the inside of the cap instead of the 0.680" diameter inside the case, generating at least 67,000 lbs of thrust. I would not be at all surprised if this is what caused the failure Kentucky Ballistics had. |
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Posted: 5/1/2021 11:24:53 PM EDT
[#40]
Quote HistoryQuoted: As several others in this thread have pointed out, the cap that threads over the barrel is a poor design. There is not enough thread engagement, you get peak strength at 1.5 x Diameter. On typical course threads that is in the ballpark of 8-12 full turns of engagement vs the 3-4 shown in pictures. Again as has been stated, 60 degree v threads should be torqued/stretched and not just hand tightened. loose threads are subject to shock loading that isn't evenly distributed, which can cause fatigue and failure/shearing. The most glaringly obvious problem with this design is the cap that threads Over the breach instead of Into the breach. - It looks like the cap has about a 1 1/4" inside diameter, it threads over the outside of the barrel and creates a pretty much airtight seal. - A normal 50 bmg is in the ballpark of 55ksi developing 20,000 lbs of bolt thrust (based on a 0.680" case I.D.), an 85ksi load would produce about 31,000 lbs of thrust which may or may not be enough to cause a failure in this gun. Not much safety factor but at least there is some. - What nobody seems to be taking into account is what happens in the event of a case rupture or even a pierced primer. All of that pressure is going to vent into that sealed up cap. That means that we now have 55,000+ psi pushing against the 1 1/4" diameter on the inside of the cap instead of the 0.680" diameter inside the case, generating at least 67,000 lbs of thrust. I would not be at all surprised if this is what caused the failure Kentucky Ballistics had. That's a good point. I was just at a 16" canon today, and indeed, the breach goes inside the barrel, not outside. As such, the SI available for PSI is lower. And, there is no way force can be exerted laterally and try to swell out that cap to slip off. |
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Posted: 5/1/2021 11:35:47 PM EDT
[#41]
Quote HistoryQuoted: As several others in this thread have pointed out, the cap that threads over the barrel is a poor design. There is not enough thread engagement, you get peak strength at 1.5 x Diameter. On typical course threads that is in the ballpark of 8-12 full turns of engagement vs the 3-4 shown in pictures. Again as has been stated, 60 degree v threads should be torqued/stretched and not just hand tightened. loose threads are subject to shock loading that isn't evenly distributed, which can cause fatigue and failure/shearing. The most glaringly obvious problem with this design is the cap that threads Over the breach instead of Into the breach. - It looks like the cap has about a 1 1/4" inside diameter, it threads over the outside of the barrel and creates a pretty much airtight seal. - A normal 50 bmg is in the ballpark of 55ksi developing 20,000 lbs of bolt thrust (based on a 0.680" case I.D.), an 85ksi load would produce about 31,000 lbs of thrust which may or may not be enough to cause a failure in this gun. Not much safety factor but at least there is some. - What nobody seems to be taking into account is what happens in the event of a case rupture or even a pierced primer. All of that pressure is going to vent into that sealed up cap. That means that we now have 55,000+ psi pushing against the 1 1/4" diameter on the inside of the cap instead of the 0.680" diameter inside the case, generating at least 67,000 lbs of thrust. I would not be at all surprised if this is what caused the failure Kentucky Ballistics had. Agree about the trapping of the gas with a cap design. That bolt thrust basically quadruples in the event of a rupture since the area quadruples with a 2x increase of the bore of your "piston". However there's nothing wrong with threads over the breach as long as it is sufficiently thick to decouple the hoop stress from the shear stress, and provides a bleed path for gases in the event of a rupture. Not much different than many rifle barrels including ARs, many bolt actions, etc... Here is the RN50 vs M2   Also people keep talking about preload on the threads but it is simply not the issue. There is ZERO preload on a M2 barrel which has much more coarse threads and are often beat to shit. You freely turn it to headspace the gun but I've never heard of a barrel being stripped from the M2 barrel extension. However the gases aren't trapped like with a cap design. |
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Posted: 5/1/2021 11:57:56 PM EDT
[#42]
Quote HistoryQuoted: Agree about the trapping of the gas with a cap design. That bolt thrust basically quadruples in the event of a rupture since the area quadruples with a 2x increase of the bore of your "piston". However there's nothing wrong with threads over the breach as long as it is sufficiently thick to decouple the hoop stress from the shear stress, provides a bleed path for gases in the event of a rupture, and you have sufficient mass/obstruction to protect the shooter in the event of a KB. Not much different than many rifle barrels including ARs, many bolt actions, etc... Here is the RN50 vs M2 https://cdn11.bigcommerce.com/s-dmbfmt5mav/images/stencil/900x1800/products/116/446/RN0025_1__72217.1604005225.jpg?c=2https://www.practicalmachinist.com/vb/attachments/f24/52000d1336761626-fs-m2hb-50cal-barrel-50cal-bbl-chamber.jpg 100% on the same page, I just wanted to point out that it is an inherently flawed and dangerous design in this case. As you pointed out the failure mode for all of those weapons is fairly safe. if the barrel/trunnion Thread fails in an m2/Ar/Bolt gun, the barrel plops to the ground infront of the gun and the user is not likely to have any life threatening injuries, or the force is contained/absorbed inside of thee receiver. The problem with the RN50 is there isn't a great way to vent gas and there is no receiver to protect the shooter. Its kind of a head scratcher as to how it made it into production. The best bet to fix it might be to add an intermediate trunnion, thread the barrel into it and make the barrel threads the weak point instead of the breach threads. That way when it fails, it fails away from your face. |
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Posted: 5/2/2021 1:05:36 AM EDT
[#43]
Quote HistoryQuoted: It's also a guy who never blamed Mark and blamed himself. If you have better evidence to prove otherwise show it, until then it's just your baseless conjecture vs the words of a stand up guy who is also praised by Mark in Mark's video today. Quote HistoryQuoted: Quoted: I'm not sure if you're aware of it but that isn't Mark Serbu. What has been quoted throughout this thread is third hand information from the guy that almost killed himself with counterfeit ammunition. It's also a guy who never blamed Mark and blamed himself. If you have better evidence to prove otherwise show it, until then it's just your baseless conjecture vs the words of a stand up guy who is also praised by Mark in Mark's video today. None of that is relevant. You stated "Serbu said..." when in fact he did not. Serbu has not stated that cap would rupture at 85Ksi, anywhere, up to this point. If you have a a first hand statement from Serbu making that claim then post it up. |
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Posted: 5/2/2021 1:47:07 AM EDT
[#45]
Quote HistoryQuoted: Ummm. If the threads let go at 85k, the pressure never got above 85k. Not saying that the potential energy in the round could not have produced pressure higher than 85k, but that doesn't change the fact previously stated. As a matter of fact, I did work on a special sabot gun that used smokeless powder to compress hydrogen/oxygen to the point of combustion. They controlled the pressure with a shear plate. When the plate sheared, they knew how much pressure was released into the bore behind the projectile. So, that is exactly how pressure peaks work. (there is gas volume/expansion rate, etc after that fact but peak pressure doesn't rise above the failure of the vessel) Besides that, if the manufacturer mentioned that the threads would do that at 85k, that is NOT an appropriate safety margin for firearms. Quote HistoryQuoted: Quoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. eta: What you are suggesting is that an 86k PSI round would have resulted in the same damage/carnage/failure seen in the video as a 100k (or higher) PSI round, and I am saying that is unequivocally wrong. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. Ummm. If the threads let go at 85k, the pressure never got above 85k. Not saying that the potential energy in the round could not have produced pressure higher than 85k, but that doesn't change the fact previously stated. As a matter of fact, I did work on a special sabot gun that used smokeless powder to compress hydrogen/oxygen to the point of combustion. They controlled the pressure with a shear plate. When the plate sheared, they knew how much pressure was released into the bore behind the projectile. So, that is exactly how pressure peaks work. (there is gas volume/expansion rate, etc after that fact but peak pressure doesn't rise above the failure of the vessel) Besides that, if the manufacturer mentioned that the threads would do that at 85k, that is NOT an appropriate safety margin for firearms. Where do you guys get this stuff? Serbu never said the rifle failed at 85K. How many pages in are we with the ARF engineers lambasting the design for letting go at 85K? He told the guy (presumably) pressures had to be AT LEAST 85K for that to happen. The rifle hasn't even been examined yet. Could the rifle be designed with more redundancy? Sure. For more money, one supposes. More weight. More complexity. The RN50's schtick... it's entire schtick, is that it's the absolute barest bones 50BMG to be had that isn't a potential hand grenade when treated properly. Most people who buy these things treat them with that in mind. You don't put Ruger Hot loads into a Virginia Dragoon, right? Well, not if you have any sense. I'm gonna go out on a limb and say that Serbu will probably alter the design in some fashion after this. But it is telling that this is the first Kaboom one of these things has ever experienced. I'll wait for the in depth analysis before I go off on whether the gun is guilty or not. |
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Posted: 5/2/2021 2:01:01 AM EDT
[#46]
Quote HistoryQuoted: None of that is relevant. You stated "Serbu said..." when in fact he did not. Serbu has not stated that cap would rupture at 85Ksi, anywhere, up to this point. If you have a a first hand statement from Serbu making that claim then post it up.  It's your conjecture vs Scott's statement on video, guess which I think is more credible?
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Posted: 5/2/2021 2:06:16 AM EDT
[#47]
Quote HistoryQuoted: My point? Information and documentation that doesn't start with "Google". Dude, straight from .mil, Army technical manual TM 43-0001-27, 9-3 (page 106): 65,000 psi http://web.archive.org/web/20071202134237/http://www.dtic.mil/dticasd/sbir/sbir032/a044a.pdf Like I said, 65 ksi from .mil or 67 ksi from CIP, it's irrelevant to this discussion but you keep arguing inane points in this thread trying to sound smart but revealing the opposite. |
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Posted: 5/2/2021 6:43:28 AM EDT
[#48]
Quote HistoryQuoted: Where do you guys get this stuff? Serbu never said the rifle failed at 85K. How many pages in are we with the ARF engineers lambasting the design for letting go at 85K? He told the guy (presumably) pressures had to be AT LEAST 85K for that to happen. The rifle hasn't even been examined yet. Could the rifle be designed with more redundancy? Sure. For more money, one supposes. More weight. More complexity. The RN50's schtick... it's entire schtick, is that it's the absolute barest bones 50BMG to be had that isn't a potential hand grenade when treated properly. Most people who buy these things treat them with that in mind. You don't put Ruger Hot loads into a Virginia Dragoon, right? Well, not if you have any sense. I'm gonna go out on a limb and say that Serbu will probably alter the design in some fashion after this. But it is telling that this is the first Kaboom one of these things has ever experienced. I'll wait for the in depth analysis before I go off on whether the gun is guilty or not. Quote HistoryQuoted: Quoted: Quoted: Its absolutely relevant, and a suggests a very simplistic understanding. This isn't 85k+ PSI of pressure that slowly built until the threads sheared....this was an immediate release/detonation of an unknown amount of pressure, far in excess of 85k psi, and its ridiculously obvious to anyone who's watched the video. You are suggesting that simply because the breech cap failed, then pressure was somehow limited to that magic number of 85k psi. This is flat out wrong. eta: What you are suggesting is that an 86k PSI round would have resulted in the same damage/carnage/failure seen in the video as a 100k (or higher) PSI round, and I am saying that is unequivocally wrong. You are absolutely determined to find fault and somehow blame this gun and its design. The owner of the rifle blames the ammo. The same guy who shot the rifle and almost lost his life blames the ammo. The guy who filmed the video and had to watch his son almost die blames the ammo. The guy who designed and built the rifle blames the ammo. Random internet guy who has no experience with the platform or ammo, blames the rifle and tries to suggest some defect. Now, as I posted before, I believe that fatigue could have been a factor if all the previously fired rounds were also overloaded far in excess of even normal proof rounds. All the evidence supports the ammo as the culprit. Period. You can debate all you want on the design of the gun, but there is no way to say 100% that he wouldn't have sustained significant injuries touching this ammo off in any other shoulder fired .50 cal rifle. Ummm. If the threads let go at 85k, the pressure never got above 85k. Not saying that the potential energy in the round could not have produced pressure higher than 85k, but that doesn't change the fact previously stated. As a matter of fact, I did work on a special sabot gun that used smokeless powder to compress hydrogen/oxygen to the point of combustion. They controlled the pressure with a shear plate. When the plate sheared, they knew how much pressure was released into the bore behind the projectile. So, that is exactly how pressure peaks work. (there is gas volume/expansion rate, etc after that fact but peak pressure doesn't rise above the failure of the vessel) Besides that, if the manufacturer mentioned that the threads would do that at 85k, that is NOT an appropriate safety margin for firearms. Where do you guys get this stuff? Serbu never said the rifle failed at 85K. How many pages in are we with the ARF engineers lambasting the design for letting go at 85K? He told the guy (presumably) pressures had to be AT LEAST 85K for that to happen. The rifle hasn't even been examined yet. Could the rifle be designed with more redundancy? Sure. For more money, one supposes. More weight. More complexity. The RN50's schtick... it's entire schtick, is that it's the absolute barest bones 50BMG to be had that isn't a potential hand grenade when treated properly. Most people who buy these things treat them with that in mind. You don't put Ruger Hot loads into a Virginia Dragoon, right? Well, not if you have any sense. I'm gonna go out on a limb and say that Serbu will probably alter the design in some fashion after this. But it is telling that this is the first Kaboom one of these things has ever experienced. I'll wait for the in depth analysis before I go off on whether the gun is guilty or not. |
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Posted: 5/2/2021 7:35:47 AM EDT
[#49]
Quote HistoryQuoted: As several others in this thread have pointed out, the cap that threads over the barrel is a poor design. There is not enough thread engagement, you get peak strength at 1.5 x Diameter. On typical course threads that is in the ballpark of 8-12 full turns of engagement vs the 3-4 shown in pictures. Again as has been stated, 60 degree v threads should be torqued/stretched and not just hand tightened. loose threads are subject to shock loading that isn't evenly distributed, which can cause fatigue and failure/shearing. The most glaringly obvious problem with this design is the cap that threads Over the breach instead of Into the breach. - It looks like the cap has about a 1 1/4" inside diameter, it threads over the outside of the barrel and creates a pretty much airtight seal. - A normal 50 bmg is in the ballpark of 55ksi developing 20,000 lbs of bolt thrust (based on a 0.680" case I.D.), an 85ksi load would produce about 31,000 lbs of thrust which may or may not be enough to cause a failure in this gun. Not much safety factor but at least there is some. - What nobody seems to be taking into account is what happens in the event of a case rupture or even a pierced primer. All of that pressure is going to vent into that sealed up cap. That means that we now have 55,000+ psi pushing against the 1 1/4" diameter on the inside of the cap instead of the 0.680" diameter inside the case, generating at least 67,000 lbs of thrust. I would not be at all surprised if this is what caused the failure Kentucky Ballistics had. You know you can put a bigger thread than needed and have less engagement, right? The design was probably based on the wall thickness around the chamber and not needing that size thread. Perhaps you can show the math that shows the number of threads was inadequate for the situation? Lemme guess, you'll avoid any actual numbers and go "BuT lOoK aT tHe PiCtuRe." I have faith that someone who can make the claims you can can show your work. |
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Posted: 5/2/2021 8:22:18 AM EDT
[#50]
If anyone is selling one cheap, let me know.
Edit. Details about the weapon here. Not a typical RN50. This was ammo related, similar to what happened in Takata airbags.  50 Cal SLAP vs Atlas Stone (340 lbs!!!) |
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